Sputtering devices are typically designed to form a metal thin film on a flat substrate. When sputtering is performed on particles by such a typical sputtering device, it is necessary to spread particles all over a thin flat container and performs sputtering on the particles in this state. With this state, typical sputtering devices can deposit target atoms sputtering from a sputtering target only on the upper surfaces of particles, disadvantageously.
In this point, Patent Literature 1 discloses a barrel sputtering apparatus that uses a tubular barrel (drum) to form coatings on fine particles. A barrel sputtering apparatus disclosed in Patent Literature 2 includes a cylindrical vacuum container that has a polygonal internal shape on a cross section and contains fine particles. This vacuum container is rotated for sputtering.